The present invention relates, in general, to the field of integrated circuit (xe2x80x9cICxe2x80x9d) devices. More particularly, the present invention relates to a negative voltage driver circuit having reduced current flow to the negative supply voltage source and overall improved reliability.
Certain dynamic random access memory (xe2x80x9cDRAMxe2x80x9d) designs require a driver circuit capable of driving an output node from a high (or xe2x80x9cpumpedxe2x80x9d) voltage level (xe2x80x9cVCCPxe2x80x9d) to a negative supply voltage level (xe2x80x9cVNWLxe2x80x9d) and back to the high voltage level. Among the constraints on such a circuit are that the current provided to the VNWL supply be reduced (due to the fact that the VNWL source is a pumped supply) and that reliable operation be effectuated by ensuring that any N-channel transistor in the driver circuit switch with a drain-to-source voltage (xe2x80x9cVDSxe2x80x9d) equal to or less than VCCP.
Particularly disclosed herein is a negative voltage driver circuit which comprises: first, second and third series coupled switching devices defining an output and intermediate nodes therebetween respectively for coupling a high voltage source to a reference voltage level. Control terminals of the first and second switching devices are coupled to a first circuit node and a control terminal of the third switching device is coupled to a second circuit node. A fourth switching device is coupled between the lower intermediate node and a negative voltage source, with a control terminal of the fourth switching device being coupled to a third circuit node. In operation, the first circuit node is activated, followed sequentially by the second and third circuit nodes, the second circuit node being deactivated substantially concurrently with the activation of the third circuit node.
Also disclosed herein is a method for operating a negative voltage driver comprising the steps of: coupling an output node to an intermediate circuit node; coupling the intermediate circuit node to a reference voltage level thereby driving the output node to substantially the reference voltage level; and decoupling the intermediate circuit node from the reference voltage level substantially concurrently with coupling the intermediate node to a negative voltage source thereby driving the output node to substantially the negative voltage source level.